The present invention is directed to colored sealed beam lamps formed from tungsten-halogen sources, a multilayer dichroic coated reflector and a multilayer dichroic coated lens.
Colored lighting is desirable in display lighting, environmental lighting, for stadium score boards, message boards and for many architectural, artistic or theatrical applications. Colored lighting is the preferred method for warning indication and direction signaling such as for traffic lighting, instrument panel lighting runway light and heliport lighting.
Currently these functions are accomplished by the use of filtered incandescent lamps. The lamps naturally emit white or yellow-white light with very high color rendering index, thus are not color selective. The lamp is contained in a fixture in all of the above applications, and the fixture is fitted with a filtering device such as a plastic lens, colored glass lens, or in some applications a changeable filtering device which holds flat filter sheets. In another filtering method, the lamp envelope is made large in relation to the wattage so that the envelope is normally cool, and the exterior is coated with a semi-transparent paint or plastic film.
Many of the above described disadvantages may be eliminated if a tungsten-halogen capsule is permanently mounted inside of a dichroic coated concave reflector, with a dichroic coated lens sealed on by glass fusing methods, frits, or by epoxies.
Such a construction is widely utilized in the Sylvania Capsylite.TM., and in most modern automobile headlights. Using such methods, lamps up to 350 Watts can be designed for lives in excess of 3000 hours.
Dichroic coatings on lamp reflectors as above have previously been used as cold mirrors or hot mirrors, or as color filters or reflectors in fixtures. See for example, Cooper, U.S. Pat. No. 3,527,974. However, the use of thin film coatings as a color filter integral to the lamp has been limited in the past because of the intense heat generated by small high wattage lamps, which causes degradation of the coating and thus the color.